The present invention pertains to a circuit arrangement for electronically generating resistor setting corresponding to a predetermined voltage. The invention pertains especially to an audio system incorporating such a circuit arrangement.
Variable electrical quantity settings are made, as a rule, by means of variable resistors. Especially where complex settings for a large number of variable resistors are concerned, it is often desired that a setting, once made, be immediately reproducible, even if other settings must be made in the meantime. Storing, in digital form, the voltage drop between one tap and one terminal on the variable resistor as the signal value for the resistance, and therefore the resistor setting, is a known method. To this end, an analog signal having a magnitude corresponding to this voltage drop is converted by an analog/digital converter into a digital signal which is storable in conventional digital memories. Reconversion of the stored signal into an analog signal is customarily effected via a digital/analog converter which produces an analog voltage at its output. This voltage can be presented to one input of a voltage-controlled amplifier which amplifies a voltage applied to it depending on the voltage at the output of the digital/analog converter, and correspondingly affects the resistor setting.
The use of voltage-controlled amplifiers, however, is very uneconomical and expensive. Also, especially when a number of such amplifiers are connected in series, such as in audio systems, such use results in unacceptable noise, restricted dynamics for the processed signals, and distortions due to nonlinearities.
For complex systems with a large number of setting regulators, for example a 28-channel audiomixer, the storage of instantaneous resistance values is thus not practically possible.
A further disadvantage to the known circuit arrangement consists in that a change in the resistor setting when the output of the digital/analog converter is being read at high frequency by a microprocessor causes a stepwise change in the output voltage which, because of the proportion of harmonics contained in audio systems, results in interfering noises unless particularly elaborate measures are taken.